Bali is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nusa Ceningan. The provincial capital, Denpasar, is the most populous city in the Lesser Sunda Islands and the second-largest, after Makassar, in Eastern Indonesia. Bali is Indonesia's main tourist destination, with a significant rise in tourism since the 1980s. Tourism-related business makes up 80% of its economy.
Bali is part of the Coral Triangle, the area with the highest biodiversity of marine species especially fish and turtles. In this area alone, over 500 reef-building coral species can be found. For comparison, this is about seven times as many as in the entire Caribbean. Bali is the home of the Subak irrigation system, a UNESCO World Heritage Site. It is also home to a unified confederation of kingdoms composed of 10 traditional royal Balinese houses, each house ruling a specific geographic area. The confederation is the successor of the Bali Kingdom. The royal houses are not recognised by the government The island of Bali lies 3.2 km (2.0 mi) east of Java, and is approximately 8 degrees south of the equator. Bali and Java are separated by the Bali Strait. East to west, the island is approximately 153 km (95 mi) wide and spans approximately 112 km (70 mi) north to south; administratively it covers 5,780 square kilometres (2,230 sq mi), or 5,577 square kilometers (2,153 sq mi) without Nusa Penida District; its population density is roughly 750 people/km² (1,900 people/sq mi).
Bali's central mountains include several peaks over 2,000 metres (6,600 feet) in elevation and active volcanoes such as Mount Batur. The highest is Mount Agung (3,031 m, 9,944 ft), known as the "mother mountain", which is an active volcano rated as one of the world's most likely sites for a massive eruption within the next 100 years. In late 2017 Mount Agung started erupting and large numbers of people were evacuated, temporarily closing the island's airport. Mountains range from centre to the eastern side, with Mount Agung the easternmost peak. Bali's volcanic nature has contributed to its exceptional fertility and its tall mountain ranges provide the high rainfall that supports the highly productive agriculture sector. South of the mountains is a broad, steadily descending area where most of Bali's large rice crop is grown. The northern side of the mountains slopes more steeply to the sea and is the main coffee-producing area of the island, along with rice, vegetables and cattle. The longest river, Ayung River, flows approximately 75 km (47 mi) (see List of rivers of Bali).
The island is surrounded by coral reefs. Beaches in the south tend to have white sand while those in the north and west have black sand. Bali has no major waterways, although the Ho River is navigable by small sampan boats. Black sand beaches between Pasut and Klatingdukuh are being developed for tourism, but apart from the seaside temple of Tanah Lot, they are not yet used for significant tourism.
The largest city is the provincial capital, Denpasar, near the southern coast. Its population is around 491,500 (2002). Bali's second-largest city is the old colonial capital, Singaraja, which is located on the north coast and is home to around 100,000 people. Other important cities include the beach resort, Kuta, which is practically part of Denpasar's urban area, and Ubud, situated at the north of Denpasar, is the island's cultural centre.
Three small islands lie to the immediate south-east and all are administratively part of the Klungkung regency of Bali: Nusa Penida, Nusa Lembongan and Nusa Ceningan. These islands are separated from Bali by the Badung Strait.
Day time temperatures at low elevations vary between 20 to 33 °C (68 to 91 °F), but the temperatures decrease significantly with increasing elevation.
The west monsoon is in place from approximately October to April, and this can bring significant rain, particularly from December to March. During the rainy season, there are comparatively fewer tourists seen in Bali. During the Easter and Christmas holidays, the weather is very unpredictable. Outside of the monsoon period, humidity is relatively low and any rain is unlikely in lowland areas. of Indonesia; however, they originated before Dutch colonisation.